John Sinnott

I was wondering why subwoofers need to be powered or have a seperate amp. Why can't your receiver power it? Would it over-tax most receivers, or does the larger size cone need more power to move it? At first, I thought the later, but then realised that there are 10" powered subs, and you can get passive towers with 10" woofers too, so that would imply that the mere size isn't the (only) reason.

And while I have you stereo gurus here, what are the pros and cons of getting a passive sub w/ seperate amp? I assume the biggest reason you'd want to do it is so that you could upgrade one compontent at a later date. Any other advantages? Disadvantages? I'm thinkng of upgrading my subwoofer, (have a Polk PSW650 165 watts w/ 2 10" cones) and was thinking of going with seperates so I could add more power at a later date if I so desired. Any thoughts?

Thanks,

-Videophile

edclem

The primary reason for separate amplification is that it reduces the load on your receiver fairly significantly. It takes more power to move a larger cone speaker (necessary to produce the low frequencies).

By using a subwoofer out jack on the back of your receiver, the amplifier stage in the receiver is only having to power the remaining portion of the bandwidth (typically above 80 Hz). With this load reduction on the receiver's amplifier stage, you will get a cleaner signal in the mid and upper frequencies.

You can test this by hooking up a pair of large woofer tower speakers to your receiver, then connecting a powered sub using the sub-out (assuming it has a crossover). You should notice that sometimes your receiver will seem to "run out of gas" when playing loud (most often bass-heavy) passages (although usually only at fairly high volume). When a powered sub is connected, this effect should be mitigated. It won't necessarily be gone, but you should notice better performance in the form of cleaner mid and high frequency sound.
HTH!

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AUDIO FREAK

Edclem is right. As a car audio installer, we have put award winning systems into cars using separate amplifiers for not only speakers and subs, but also for front, rear, and center. The last job we did used 7 different amps to power each set of speakers and separate them into highs, low, and mids. In a home theater application, the more stress that you can relieve from the receiver or processer either by bi-amplification or using powered subs, the better the sound.